Why waterlogging persisted in Chennai’s T Nagar

T Nagar, an area included in the Smart Cities Mission, saw heavy water logging after the rains, despite the Chennai Corporation spending crores on building stormwater drains and improving canals in the area.
Commuters wade through a water-logged street following heavy rain, in Chennai
Commuters wade through a water-logged street following heavy rain, in Chennai
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In 2018, as part of the Smart Cities Mission project, the Greater Chennai Corporation (GCC) spent about Rs 200 crore to make Pondy Bazaar in Chennai’s T Nagar flood-resilient. This was one of the many makeover aspects proposed for Pondy Bazaar. Why then, and how, did T Nagar get flooded since Chennai started receiving moderate or heavy rains from November 6? This question has been doing the rounds on Twitter, with users sharing videos of a waterlogged Pondy Bazaar.

As a neighbourhood, T Nagar had been identified for area-based development under the Union Government’s Smart Cities Mission. A year after the Chennai Corporation spent crores to develop Pondy Bazaar, it was reopened with a new Rs 39 crore pedestrian plaza and wider pavements. However, on Sunday, November 7, rains drowned the Smart City area. Many parts of T Nagar, including Bashyam Road, Pondy Bazaar, GN Chetty Road and smaller streets such as Bazullah street, Habibullah Street, Giri road, Usman Road, among others, have been witnessing waterlogging for the past two days now.

A recent, quick ground inspection by J Karunanithi, the DMK MLA from T Nagar constituency, and GCC Commissioner Gagandeep Singh Bedi found the source of the flooding — the Mambalam Canal. They also identified the culprit — the Smart City project work.

According to multiple reports, of Rs 200 crore from the Smart Cities fund to make Pondy Bazaar flood-resistant, the Chennai Corporation used Rs 110 crore to construct stormwater drains in the neighbourhood and Rs 80 crore to develop the Mambalam Canal, an age-old waterway into which stormwater usually drains.

However, the concrete debris from the Smart City project works was being dumped into the canal, so much so that there was no way for the water to flow, especially after the area saw 20 centimetres of rainfall on November 7.

The debris was dumped along a 1.7 km stretch of the canal from Valluvar Kottam to GN Chetty road in T Nagar. Once the source of the flooding was identified, the Chennai Corporation officials, on Wednesday, November 10, began widening the Mambalam canal, connecting inlets and clearing out all debris and garbage to allow free flow of water.

Speaking to TNM, DMK MLA Karunanithi, said that he, along with GCC Commissioner Gagandeep Singh Bedi and their teams, surveyed every street on November 8 and 9, to understand why the rainwater was not draining out in T Nagar, especially the GN Chetty Road, Boag Road and Bazullah Road.

“We went from one street to another to understand why the water was stagnant and how the water flowed. We had used motor pumps to suck water off the Bazullah Road and other streets. However, the water strayed into the neighbouring street in the process. It simply would not recede or drain out. Finally, we reached the Mambalam Canal and found that the debris from the renovation work was blocking the canal and had been causing the flooding,” the MLA J Karunanithi told TNM.

After nearly three days of intense waterlogging, officials from the GCC started widening the Mambalam Canal on Wednesday afternoon, November 10, to let the water flow. The Smart City work on canal improvement has also been stopped temporarily.

Poorly built stormwater drains

While Mambalam Canal blockage is part of the problem, stormwater drains (SWDs) and their poor design in T Nagar is the other issue. The Chennai Corporation spent a total of Rs 110 crore between 2019 and 2020 to construct stormwater drains in T Nagar as part of the area-based development works of the Smart City project. However, the drains have been badly designed without studying T Nagar landmass/topography and without proper elevations studies done, said experts.

“When stormwater drains are being built, say about 3-4 square kms, there are many aspects to factor in. There should be gravity for water to flow into stormwater drains. This means that the drain has to be constructed at a level lower than the ground elevation.  This is why elevation studies are important,” explained S Janakaraja, a climate activist and former professor at the Madras Institute of Development Studies (MIDS). He also alleged that SWDs in T Nagar were built so without proper alignment.

“Before building the stormwater drains, he said, there are several factors one must look into — the direction in which the water flows, the ground elevation in the region, quantum of rainfall typically received, and the carrying capacity of the drain. “After it is built, you have to frequently monitor the SWDs to ensure they are not choked with garbage or other debris. People tend to misuse these drains by using them as a sewage system or a garbage dumping spot. So without monitoring, most of the drains will remain blocked,” said Janakaraja.

The junction areas (where two drain lines meet) of these drains also have to be cleaned and maintained regularly. TNM also contacted Raj Cherubal, CEO of Chennai Smart City, but he wished not to offer a comment on the issue.

Meanwhile, Tamil Nadu Chief Minister MK Stalin visited GN Chetty, Bazullah Road and other parts of T Nagar that were waterlogged. The Chief Minister has also promised a detailed investigation on why the Smart City areas were flooded.

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